Surface shape recognition sensor

ABSTRACT

A detection element ( 1 A) having a detection electrode ( 11 A) connected to a surface shape detection unit ( 2 ) and a detection electrode ( 12 A) connected to a common potential, and a detection element ( 1 B) having a detection electrode ( 11 B) connected to the surface shape detection unit ( 2 ) and a detection electrode ( 12 B) connected to a biometric recognition unit ( 3 ) are arranged. The surface shape detection unit ( 2 ) outputs a signal representing the three-dimensional pattern of the surface shape corresponding to the contact portion to each detection element on the basis of individual capacitances obtained from the detection elements ( 1 A,  1 B). The biometric recognition unit ( 3 ) determines whether an object ( 9 ) is a living body, on the basis of a signal corresponding to the impedance of the object ( 9 ) connected between the detection electrode ( 12 B) of the detection element ( 1 B) and the detection electrode ( 12 A) of the detection element ( 1 A).

The present patent application is a non-provisional application ofInternational Application No. PCT/JP2004/011606, filed Aug. 12, 2004.

TECHNICAL FIELD

The present invention relates to a surface shape recognition sensordevice and, more particularly, to a biometric recognition technique forrecognizing a person by detecting biometric information such as afingerprint from an object.

BACKGROUND ART

As the information-oriented society becomes more advanced, technologiesfor security protection of information processing systems have beendeveloped. For example, ID cards are conventionally used to controlaccess to computer rooms. However, the cards can be missing or stolen athigh probability. To prevent this, introduction of personal recognitionsystems is starting, in which the fingerprint or the like of each personis registered in advance, and the fingerprint unique to each person iscollated when he/she accesses the room, instead of using the ID cards.

Such a personal recognition system sometimes passes, e.g., a replica ofa registered fingerprint. Hence, the personal recognition system mustalso recognize that the object is a living body in addition tofingerprint collation.

First Prior Art

The first prior art will be described which detects that an object is aliving body (e.g., Japanese Patent Laid-Open Nos. 2001-12980 and2001-62204). In a fingerprint detection device according to the firstprior art, the absolute capacitance of a finger placed on the sensorsurface is measured. For this purpose, using the sensor structure shownin FIGS. 22A to 22C, finger detection is done by a capacitive grid orcapacitive plate which is arranged on the upper side of a finger sensorelectrode.

A finger detection sensor electrode is electrically insulated from afingerprint sensor electrode. Finger detection sensor electrodes may bearranged between fingerprint detection sensor electrodes 71 and ondifferent surfaces, like finger detection sensor electrodes 72A shown inFIG. 22A. Alternatively, the finger detection sensor electrodes mayreplace the fingerprint detection sensor electrodes 71 and be arrangedon the same surface, like a finger detection sensor electrodes 72B.

As shown in FIG. 22B, a finger detection sensor electrode 72C may bearranged on the upper side of the fingerprint detection sensorelectrodes 71 while sandwiching a protective film 73A and covered with aprotective film 73B. As shown in FIG. 22C, a finger detection sensorelectrode 72D may be formed on the upper side of the fingerprintdetection sensor electrodes 71 to be exposed through a protective film73C.

On the basis of the finger capacitance thus measured, finger detectionis done by the circuit arrangement shown in FIG. 23. The capacitancegenerated in a finger detection sensor electrode 81 is converted into arepresentative frequency by a representative frequency converter 82 andcompared with a reference frequency or frequency range 83 by a frequencycomparator 84 to determine whether the measured capacitance matches thepredicted biological characteristic of living skin tissue. Accordingly,advanced finger detection is implemented.

Second Prior Art

The second prior art to detect that an object is a living body will bedescribed (e.g., Japanese Patent Laid-Open No. 11-185020). In anindividual authentication sensor according to the second prior art, aplurality of measurement electrodes 91 are arranged on a semiconductorsubstrate, and a common electrode 92 is arranged around the measuringelectrodes 91, as shown in FIG. 24. Switching elements which selectivelyconnect the respective measuring electrodes 91 to an I-V conversioncircuit (detection circuit) 96 can be selected by scanning a row shiftregister 95 and column shift register 94.

A switch means 92A is arranged, which switches the common electrode 92between the power supply and ground in measuring to detect contact of anauthentication target to the measuring electrodes 91 or in standbywithout the measurement.

When the common electrode 92 is spaced apart from the measuringelectrodes 91, the presence/absence of a characteristic feature of aliving body can be detected between a fingertip and a body part exceptthe finger and, for example, the back of the hand. More specifically,this technique uses the fact that the distance between the electrodesdoes not depend on the measurement result because the internalresistance of the finger is low.

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

In the above-described prior arts, however, no accurate biometricrecognition can be executed because of a potential variation induced tothe object. In addition, a detection element for biometric recognitionmust be arranged independently of the detection element for surfaceshape detection. This results in an increase in layout area andmanufacturing cost per chip.

For example, in the first prior art, when the capacitance is measured bythe finger detection sensor electrode, an error occurs in capacitancemeasurement due to the potential variation induced to the finger becausethe potential of the finger is not fixed. For this reason, thedetermination result is inaccurate, and no sufficient security can beensured. In addition, whether the object is a living body is determinedby converting the capacitance of the finger into a frequency ormeasuring the resistance of the finger. Since only the capacitancecomponent and resistance component of the impedance of the finger cannotbe detected, even an artificial finger made of an adjusted material isrecognized as a living body.

Furthermore, when the capacitance-to-frequency converter to process thecapacitance of the finger or the resistance measuring device to measurethe resistance of the finger and the comparison circuit are formed byconventional circuits, external components are necessary. For thisreason, the number of components increases, and it becomes difficult toreduce the device size. In addition, no sufficient security can beensured when the detection signal is read from the interconnection toconnect the components. In this case, the condition to determine aliving body can easily be estimated from the element value of theexternal component.

In the above-described first prior art, in biometric authentication, thelayout of the sensor electrodes to detect the electrical characteristicfrom the object and the circuit portion to execute biometric recognitionon the basis of the signals from the sensor electrodes is not taken intoconsideration. In some layouts of the sensor electrodes and circuitportion, no sufficient determination accuracy or security of biometricrecognition can be obtained.

For example, referring to FIGS. 22A to 22C, the finger detection circuitshown in FIG. 23 is not arranged near the finger detection sensorelectrodes 71A, 71B, 71C, and 71D. When the interconnection to connectthe finger detection sensor electrodes to the finger detection circuitis relatively long, the parasitic capacitance or noise of theinterconnection increases. Hence, the capacitance of the object cannotaccurately be detected, and the biometric recognition accuracydecreases.

In addition, whether the object is a living body is determined byconverting the capacitance of the finger into a frequency or measuringthe resistance of the finger. Since only the capacitance component andresistance component of the impedance of the finger cannot be detected,even an artificial finger made of an adjusted material is recognized asa living body.

In the second prior art, as shown in FIG. 24, a second common electrode93 is arranged independently of the fingerprint sensor array. Thisresults in an increase in layout area and manufacturing cost per chip.The object is determined as a living body when the distance between theelectrodes 91 is changed, and the resistance does not change. When theinternal resistance of an artificial finger is low, it is recognized asa living body. The resistance of a finger is measured. As in the firstprior art, since only the capacitance component and resistance componentof the impedance of the finger cannot be detected even an artificialfinger made of an adjusted material is recognized as a living body.

The present invention has been made to solve these problems, and has asits object to provide a surface shape recognition sensor device whichcan accurately execute biometric recognition by suppressing thepotential variation induced to the object and easily implement on-chipdevice formation by avoiding any increase in device size due to additionof a detection electrode.

It is another object of the present invention to provide a surface shaperecognition sensor device which can obtain sufficient determinationaccuracy and security of biometric recognition and easily implementon-chip device formation by avoiding any increase in device size.

Means of Solution to the Problems

In order to achieve the above objects, a surface shape recognitionsensor device according to the present invention comprises a pluralityof detection elements which are two-dimensionally arranged, a firstdetection electrode which is included in each detection element andcomes into contact with an object through an insulating film to generatea capacitance corresponding to a three-dimensional pattern of a surfaceshape of the object, a second detection electrode which is included ineach detection element and comes into electrical contact with thedetection element, a surface shape detection unit which detects thethree-dimensional pattern of the surface shape as an output from thedetection element on the basis of the capacitance obtained through thefirst detection electrode of the detection element, and a biometricrecognition unit which determines whether the object is a living body,on the basis of a signal corresponding to an impedance of the objectconnected between the second detection electrodes included in at least afirst detection element and second detection element of the detectionelements. The second detection electrode of the first detection elementis connected to a predetermined common potential, and the seconddetection electrode of the second detection element is connected to thebiometric recognition unit.

The device may further comprise a third detection element which isarranged between the first detection element and the second detectionelement and has the first detection electrode connected to the surfaceshape detection unit and the second detection electrode set in ahigh-impedance state.

The device may further comprise a switch which is connected between thecommon potential and the second detection electrode of the thirddetection element to disconnect the second detection electrode from thecommon potential when the biometric recognition unit executes biometricdetermination of the object and short-circuit the second detectionelectrode to the common potential when the surface shape detection unitdetects the surface shape.

The device may further comprise a third detection element which isarranged between the first detection element and the second detectionelement, has the first detection electrode connected to the surfaceshape detection unit and the second detection electrode connected to thecommon potential, and includes an insulating film which insulates thesecond detection electrode from the object.

The device may further comprise a switch which is connected between thebiometric recognition unit and the second detection electrode of thesecond detection element to selectively connect the second detectionelectrode to the biometric recognition unit when the biometricrecognition unit executes biometric determination of the object andselectively connect the second detection electrode to the commonpotential when the surface shape detection unit detects the surfaceshape.

The sensor surface may have a structure comprising a band-shaped seconddetection region which includes a plurality of second detection elementsarranged adjacent to each other and is arranged to cross a center of thedetection surface, two band-shaped third detection regions which includea plurality of first detection elements arranged adjacent to each otherand are arranged on both sides of the second detection region, and twoband-shaped first detection regions which include a plurality of thirddetection elements arranged adjacent to each other and are arrangedoutside the third detection regions.

The sensor surface may have another structure comprising a seconddetection region which includes a plurality of second detection elementsarranged adjacent to each other and is arranged at a center of thedetection surface, a third detection region which includes a pluralityof first detection elements arranged adjacent to each other and isarranged to surround an entire periphery of the second detection region,and a first detection region which includes a plurality of thirddetection elements arranged adjacent to each other and is arranged tosurround an entire periphery of the third detection region.

The sensor surface may have a structure comprising a band-shaped seconddetection region which includes a plurality of second detection elementsarranged adjacent to each other and is arranged to cross a center of thedetection surface, and two band-shaped first detection regions whichinclude a plurality of first detection elements arranged adjacent toeach other and are arranged on both sides of the second detectionregion.

The sensor surface may have another structure comprising a seconddetection region which includes a plurality of second detection elementsarranged adjacent to each other and is arranged at a center of thedetection surface, and a first detection region which includes aplurality of first detection elements arranged adjacent to each otherand is arranged to surround an entire periphery of the second detectionregion.

The biometric recognition unit may include a response signal generationunit which applies a predetermined supply signal to the detectionelement and outputs, as a response signal, a signal whose phase andamplitude have changed in accordance with an impedance of the objectwhich is in contact through the detection element, a waveforminformation detection unit which detects, as waveform information, oneof the phase and amplitude representing a waveform of the responsesignal and outputs a detection signal representing the waveforminformation, and a biometric determination unit which determines on thebasis of the waveform information contained in the detection signalwhether the detection signal is a living body.

According to the present invention, a surface shape recognition sensordevice comprises a plurality of capacitance detection units which arearranged in a grid shape to cause a detection element to detect acapacitance generated with respect to an object and output a capacitancesignal representing a value of the capacitance, detection elements whichare arranged near the capacitance detection units, a plurality ofcontrol lines which connect, of the capacitance detection units,capacitance detection units arranged in a column direction, a pluralityof data lines which connect, of the capacitance detection units,capacitance detection units arranged in a row direction, a columnselector which sequentially selects one of the control lines to selecteach capacitance detection unit connected to the control line, a firstA/D conversion unit which is arranged for each data line andA/D-converts the capacitance signal, which is output from eachcapacitance detection unit selected by the column selector to the dataline, into three-dimensional data and outputs the three-dimensionaldata, a row selector which sequentially selects the three-dimensionaldata obtained from the first A/D conversion unit for each data line andoutputs the three-dimensional data as surface shape data representing asurface shape of the object, an impedance detection unit which isarranged together with a detection element as a pair in place of one ofthe capacitance detection units and comes into electrical contact withthe object through the detection element to detect an impedance of theobject and outputs a detection signal corresponding to the impedance,and

a biometric determination unit which determines on the basis of thedetection signal from the impedance detection unit whether the object isa living body. The biometric recognition unit comprises a responsesignal generation unit which applies a predetermined supply signal tothe detection element and outputs, as a response signal, a signal whosephase and amplitude have changed in accordance with an impedance of theobject which is in electrical contact through the detection element, anda waveform information detection unit which detects, as waveforminformation, one of the phase and amplitude representing a waveform ofthe response signal and outputs a detection signal representing thewaveform information. The biometric determination unit executesdetermination on the basis of whether the waveform information containedin the detection signal falls within a reference range of the waveforminformation which indicates an authentic living body.

The device may further comprise an individual control line which isconnected to the impedance detection unit, an individual data line whichis connected to the impedance detection unit, a control unit whichselects the impedance detection unit by selecting the individual controlline, and a second A/D conversion unit which outputs, as determinationdata, the waveform information contained in the detection signal outputfrom the impedance detection unit to the individual data line, whereinthe impedance detection unit outputs the detection signal representingthe waveform information corresponding to the impedance of the object tothe individual data line in accordance with selection by the controlunit through the individual control line, and the biometricdetermination unit executes determination on the basis of the waveforminformation contained in the determination data from the second A/Dconversion unit.

The device may further comprise an individual control line which isconnected to the impedance detection unit, and a control unit whichselects the impedance detection unit by selecting the individual controlline, wherein the impedance detection unit is connected to one of thedata lines and outputs the detection signal representing the waveforminformation corresponding to the impedance of the object to the dataline in accordance with selection by the control unit through theindividual control line, and the biometric determination unit executesdetermination on the basis of the waveform information contained indetermination data which is obtained by causing the first A/D conversionunit to A/D-convert the detection signal output to the data line.

The impedance detection unit may be connected to one of the controllines and one of the data lines and output the detection signal to thedata line in accordance with selection by the selector, and thebiometric determination unit may execute determination on the basis ofthe waveform information contained in determination data which isobtained by causing the first A/D conversion unit to A/D-convert thedetection signal output to the data line.

The device may comprise a plurality of impedance detection units whichare arranged in place of different capacitance detection units.

Effects of the Invention

According to the present invention, a first detection element having afirst detection electrode connected to a surface shape detection unitand a second detection electrode connected to a common potential, and asecond detection element having a first detection electrode connected tothe surface shape detection unit and a second detection electrodeconnected to a biometric recognition unit are arranged. The surfaceshape detection unit detects the surface shape on the basis ofindividual capacitances obtained from the first and second detectionelements. The biometric recognition unit executes biometric recognitionon the basis of a signal corresponding to the impedance of an objectconnected between the second detection electrode of the second detectionelement and the second detection electrode of the first detectionelement. With this arrangement, accurate biometric recognition can beexecuted while suppressing a potential variation induced to the object.In addition, on-chip device formation can easily be implemented byavoiding any increase in device size due to addition of a detectionelectrode.

According to the present invention, the capacitance detection units forsurface shape detection are arranged in a matrix together with thedetection elements. In place of one of the capacitance detection units,the impedance detection unit for biometric recognition is arrangedtogether with the detection element as a pair. With this arrangement,the interconnection which connects the detection element for biometricrecognition to the impedance detection unit to drive the detectionelement can be very short. Since the parasitic capacitance or noise ofthis interconnection can be reduced, the impedance of the object canaccurately be detected. Hence, a high determination accuracy can beobtained in biometric recognition.

In the impedance detection unit, a predetermined supply signal isapplied to the detection element. A signal whose phase and amplitudeshave changed in accordance with the impedance of the object is acquiredas a response signal. Waveform information containing the phase oramplitude representing the waveform of the response signal is detectedand output as a detection signal. Determination is done by the biometricdetermination unit on the basis of determination data obtained byA/D-converting the detection signal. For example, a resistive element orcapacitive element which requires a large area is not always necessary,unlike the prior art. Waveform information representing the impedanceunique to the object can be detected in detail by a very simple circuitarrangement such as a general comparator and logic circuit. Hence, sizereduction of the surface shape recognition sensor device and on-chipdevice formation can easily be implemented. In addition, the externalcomponent such as a resistive element or capacitive element isunnecessary. Since any decrease in security level caused by the externalcomponent can be avoided, sufficient security can be obtained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing the outer appearance of a surfaceshape recognition sensor device according to an embodiment of thepresent invention;

FIG. 2 is a block diagram showing the arrangement of a surface shaperecognition sensor device according to the first embodiment of thepresent invention;

FIG. 3 is a circuit diagram showing the arrangement of a sensor cellused in a surface shape detection unit shown in FIG. 2;

FIGS. 4A to 4C are timing charts showing the waveforms of signals of therespective parts shown in FIG. 3;

FIG. 5 is a block diagram showing the arrangement of a biometricrecognition unit shown in FIG. 2;

FIGS. 6A to 6D are timing charts showing signal waveforms in phasedifference detection by the biometric recognition unit shown in FIG. 5;

FIGS. 7A and 7B are timing charts showing signal waveforms in amplitudedetection by the biometric recognition unit shown in FIG. 5;

FIGS. 8A and 8B are explanatory views showing the arrangement ofdetection elements shown in FIG. 2;

FIG. 9 is a block diagram showing the arrangement of a surface shaperecognition sensor device according to the second embodiment of thepresent invention;

FIGS. 10A and 10B are explanatory views showing the arrangement ofdetection elements shown in FIG. 9;

FIG. 11 is a block diagram showing the arrangement of a surface shaperecognition sensor device according to the third embodiment of thepresent invention;

FIG. 12 is a block diagram showing the arrangement of a surface shaperecognition sensor device according to the fourth embodiment of thepresent invention;

FIGS. 13A and 13B are explanatory views showing the arrangement ofdetection elements shown in FIG. 12;

FIG. 14 is a block diagram showing the arrangement of a surface shaperecognition sensor device according to the fifth embodiment of thepresent invention;

FIGS. 15A and 15B are explanatory views showing the sensor surfacestructure of a surface shape recognition sensor device according to thesixth embodiment of the present invention;

FIG. 16 is a block diagram showing another embodiment of the biometricrecognition unit shown in FIG. 2;

FIGS. 17A to 17D are timing charts showing signal waveforms in phasedifference detection by the biometric recognition unit shown in FIG. 16;

FIGS. 18A and 18B are timing charts showing signal waveforms inamplitude detection by the biometric recognition unit shown in FIG. 16;

FIG. 19 is a block diagram showing the arrangement of a surface shaperecognition sensor device according to the seventh embodiment of thepresent invention;

FIG. 20 is a block diagram showing the arrangement of a surface shaperecognition sensor device according to the eighth embodiment of thepresent invention;

FIG. 21 is a block diagram showing the arrangement of a surface shaperecognition sensor device according to the ninth embodiment of thepresent invention;

FIGS. 22A to 22C are block diagrams showing the sensor structures of afingerprint detection device according to the first prior art;

FIG. 23 is a block diagram showing the main part of the fingerprintdetection device according to the first prior art; and

FIG. 24 is a block diagram showing an individual authentication sensoraccording to the second prior art.

BEST MODE FOR CARRYING OUT THE INVENTION

The embodiments of the present invention will be described next withreference to the accompanying drawings.

FIG. 1 is a perspective view showing the outer appearance of a surfaceshape recognition sensor device according to an embodiment of thepresent invention. This surface shape recognition sensor device is usedas a circuit device which detects the surface shape of an object in asurface shape recognition device which authenticates an object bycomparing and collating the shape of the collation target surface of theobject having, e.g., a fine three-dimensional pattern with collationdata. As shown in FIG. 1, a surface shape recognition sensor device 10includes a number of fine detection elements 1 arrangedtwo-dimensionally (in an array or grid shape) on an LSI chip.

When an object 9 such as a finger is brought into contact with a sensorsurface 8 of the surface shape recognition sensor device 10, the surfaceof the object 9, and in this case, the three-dimensional shape of thefingerprint is individually detected through each detection element 1,and surface shape data representing the surface shape of the object isoutput.

In the present invention, biometric recognition is executed by using thedetection elements 1 for surface shape detection.

First Embodiment

A surface shape recognition sensor device according to the firstembodiment of the present invention will be described next withreference to FIG. 2. FIG. 2 is a block diagram showing the arrangementof the surface shape recognition sensor device according to the firstembodiment of the present invention.

A surface shape recognition sensor device 10 includes detection elements1A and 1B, surface shape detection unit 2, and biometric recognitionunit 3.

The detection element 1A has a detection electrode 11A which forms anelectrostatic capacitance with respect to an object 9 through aninsulating film, and a detection electrode 12A which comes intoelectrical contact with the object 9. The detection electrode 11A isconnected to the surface shape detection unit 2. The detection electrode12A is connected to a common potential such as a ground potential. Thecommon potential is supplied from a predetermined supply circuit unit(not shown) such as a power supply circuit at a predetermined potential(low impedance). The detection element 1B has a detection electrode 11Bwhich forms an electrostatic capacitance with respect to the object 9through the insulating film, and a detection electrode 12B which comesinto electrical contact with the object 9. The detection electrode 11Bis connected to the surface shape detection unit 2. The detectionelectrode 12B is connected to the biometric recognition unit 3.

The surface shape detection unit 2 is a circuit unit which outputssurface shape data 2S representing the three-dimensional shape of thesurface of the object 9 on the basis of the electrostatic capacitancesgenerated between the object 9 and the detection electrodes 11A and 11Bof the detection elements 1A and 1B.

The biometric recognition unit 3 is a circuit unit which determineswhether the object 9 is a living body, on the basis of the impedance ofthe object 9 connected between the detection electrode 12B of thedetection element 1B and the detection electrode 12A of the detectionelement 1A.

The operation of the surface shape recognition sensor device accordingto this embodiment will be described next. The surface shape recognitionsensor device 10 has, as operations, the surface shape detectionoperation of detecting the surface shape of the object 9 and biometricrecognition operation of executing biometric recognition of the object9. One of these operations is selectively executed under the control ofa host apparatus (not shown).

In the surface shape detection operation, on the basis of the magnitudeof the electrostatic capacitance formed between the object 9 and thedetection electrode 11A of the detection element 1A, the surface shapedetection unit 2 generates a signal representing the surface shape ofthe object 9 at the position of the detection element 1A and outputs thesignal as the surface shape data 2S.

Even for the detection element 1B, on the basis of the magnitude of theelectrostatic capacitance formed between the object 9 and the detectionelectrode 11B, the surface shape detection unit 2 generates the surfaceshape data 2S representing the three-dimensional shape of the surface ofthe object 9 and outputs the data as the surface shape data 2S.

Since the object 9 is connected to the common potential through thedetection electrode 12A of the detection element 1A, the electrostaticcapacitances formed by the detection electrodes 11A and 11B stabilize,and the surface shape data 2S with minimum noise is obtained.

On the other hand, in the biometric recognition operation, since theobject 9 is connected to the common potential through the detectionelectrode 12A of the detection element 1A, a current path is formed fromthe detection electrode 12B of the detection element 1B to the detectionelectrode 12A of the detection element 1A, i.e., the common potentialthrough the object 9.

On the basis of whether the impedance value unique to the object 9present in the current path falls within a reference range whichindicates the impedance of an authentic living body, the biometricrecognition unit 3 determines whether the object 9 is a living body.

At this time, the biometric recognition unit 3 executes biometricrecognition by using a signal which changes depending on the impedanceof the object 9. Since the object 9 is connected to the common potentialthrough the detection electrode 12A of the detection element 1A, thepotential variation by induction to the object 9 is suppressed. Hence, astable signal is obtained, and accurate biometric recognition isimplemented.

As described above, in this embodiment, the detection element 1A havingthe detection electrode 11A connected to the surface shape detectionunit 2 and the detection electrode 12A connected to the common potentialand the detection element 1B having the detection electrode 11Bconnected to the surface shape detection unit 2 and the detectionelectrode 12B connected to the biometric recognition unit 3 arearranged. The surface shape detection unit 2 outputs the signalsrepresenting the three-dimensional patterns of surface shapescorresponding to the contact positions to the detection elements 1A and1B on the basis of the capacitances obtained from the detection elements1A and 1B. The biometric recognition unit 3 determines whether theobject 9 is a living body on the basis of the signal corresponding tothe impedance of the object 9 connected between the detection electrode12B of the detection element 1B and the detection electrode 12A of thedetection element 1A.

Since the object 9 is connected to the common potential through thedetection electrode 12A of the detection element 1A, accurate biometricrecognition can be executed by suppressing the potential variationinduced to the object 9. In addition, surface shape data with minimumnoise can be obtained.

Since the detection elements are used for both the surface shapedetection operation and the biometric recognition operation, nodetection element for biometric recognition need be arrangedindependently of the detection elements to detect the surface shape.Hence, any increase in layout area and manufacturing cost per chip canbe avoided. Biometric recognition can be executed in addition to surfaceshape detection of the object without increasing the device size.Accordingly, on-chip device formation can easily be implemented.

In the example shown in FIG. 2, one detection element 1A and onedetection element 1B are used. However, this is a minimum arrangementnecessary for executing biometric recognition, and the present inventionis not limited to this. Actually, a number of detection elements 1A areused to obtain the surface shape data representing the surface shape ofthe object 9 by the surface shape detection unit 2. In addition, anumber of detection elements 1B are used to stably detect the impedanceof the object 9 by the biometric recognition unit 3.

Arrangement of Surface Shape Detection Unit

The detailed arrangement of the surface shape detection unit 2 used inthe surface shape recognition sensor device according to this embodimentwill be described next with reference to FIGS. 3 and 4A to 4C. FIG. 3 isa circuit diagram showing the arrangement of a sensor cell used in thesurface shape detection unit 2. FIGS. 4A to 4C are timing charts showingthe signals of the respective parts shown in FIG. 3. A known technique(e.g., Japanese Patent Laid-Open No. 2000-28311) is used for thedetailed example of the surface shape detection unit 2.

In the surface shape detection unit 2, a sensor cell which converts acapacitance detected in accordance with the surface shape of the object9 by a detection element 1 into a predetermined output signal isarranged for each detection element 1. The sensor cell includes a signalgeneration circuit 21 which generates a signal corresponding to thecapacitance of the detection element 1, a signal amplification circuit22 which amplifies the level of the signal by the signal generationcircuit 21 and outputs the signal, and an output circuit 23 whichconverts the output signal from the signal amplification circuit 22 intoa desired signal and outputs it.

Referring to FIG. 3, an electrostatic capacitance C_(F) is formedbetween a detection electrode 11 and the object 9. At a node N_(1A), avoltage signal ΔV_(I) corresponding to C_(F) is generated by the signalgeneration circuit 21. The voltage signal ΔV_(I) is amplified to avoltage signal ΔV₀ by the signal amplification circuit 22. A voltagesignal V_(OUT) corresponding to the magnitude of the voltage signal ΔV₀is output from the output circuit 23 as the output signal. Referencesymbols C_(P1A) and C_(P2A) denote parasitic capacitances.

As shown in FIGS. 4A to 4C, before time T1, a sensor circuit controlsignal PRE₀ is controlled to a power supply voltage V_(DD) so thatQ_(1A) is turned off. A sensor circuit control signal RE is controlledto a voltage of 0 V so that Q_(3A) is OFF, and the node N_(1A) is set to0 V. At the time T1, the signal PRE₀ is controlled to 0 V so that Q_(1A)is turned on. A node N_(2A) rises to V_(DD), and the node N_(1A) risesto a value less than a bias voltage V_(G) by a threshold voltage V_(TH)of Q_(2A). At time T2, the signals PRE₀ and RE are controlled to V_(DD)so that Q_(1A) is turned off, and Q_(3A) is turned on. Accordingly, thecharges stored in the capacitances C_(F) and C_(P1A) are discharged, andthe potential of the node N_(1A) decreases.

During only the period when the potential of the node N_(2A) issufficiently high, the charges stored in the capacitance C_(P2A) areabruptly discharged. When the potential of the node N_(2A) decreases toalmost the potential of the node N_(1A), the potentials of the nodesN_(1A) and N_(2A) gradually decrease. At time T3 after the elapse of Δtfrom the time T2, the signal RE is controlled to 0 V to turn off Q_(3A).The potential V_(DD)−ΔV of the node N_(2A) at that time is maintained,amplified, and output as V_(OUT). Accordingly, the voltage ΔV_(OUT)corresponding to the value of the electrostatic capacitance C_(F) isobtained. When this voltage signal is processed, the three-dimensionalpattern of the surface shape can be recognized.

Arrangement of Biometric Recognition Unit

The detailed arrangement of the biometric recognition unit 3 used in thesurface shape recognition sensor device according to this embodimentwill be described next with reference to FIG. 5. FIG. 5 is a blockdiagram showing the arrangement of the biometric recognition unit.

The biometric recognition unit 3 includes a supply signal generationunit 31, response signal generation unit 32, waveform informationdetection unit 33, and biometric determination unit 34.

The detection elements 1A and 1B come into electrical contact with theobject 9 through the detection electrodes 12A and 12B to connect acapacitance component Cf and resistance component Rf of the impedance ofthe object 9 to the response signal generation unit 32. The supplysignal generation unit 31 generates a supply signal 31S such as a sinewave of a predetermined frequency and outputs it to the response signalgeneration unit 32. The response signal generation unit 32 supplies thesupply signal 31S from the supply signal generation unit 31 to thedetection electrode 12B of the detection element 1B and outputs, to thewaveform information detection unit 33, a response signal 32S whichchanges depending on the output impedance of the detection element 1B,i.e., the capacitance component and resistance component of theimpedance of the object 9.

The waveform information detection unit 33 detects the amplitude or thephase difference of the supply signal 31S on the basis of the waveformindicated by the response signal 32S from the response signal generationunit 32 and outputs, to the biometric determination unit 34, a detectionsignal 33S containing waveform information representing the phasedifference or amplitude. On the basis of the waveform informationcontained in the detection signal 33S from the waveform informationdetection unit 33, the biometric determination unit 34 determineswhether the object 9 is a living body, and outputs a recognition result3S.

When the object 9 comes into contact with the detection elements 1A and1B, the supply signal 31S applied from the supply signal generation unit31 to the detection elements 1A and 1B changes depending on theimpedance characteristic, i.e., the capacitance component and resistancecomponent unique to the object 9 and is output from the response signalgeneration unit 32 as the response signal 32S. The waveform informationdetection unit 33 detects the amplitude or phase difference of theresponse signal 32S. The detection signal 33S containing the informationrepresenting the detection result is output to the biometricdetermination unit 34.

FIGS. 6A to 6D show examples of signal waveforms in phase differencedetection. When a sine wave with its center at the common potential suchas the ground potential is used as the supply signal 31S, the phase ofthe response signal 32S changes in accordance with the impedance of theobject 9. When a signal synchronized with the supply signal 31S is usedas the reference signal, and its phase is compared with the phase of theresponse signal 32S by the waveform information detection unit 33, thedetection signal 33S having a pulse width corresponding to, e.g., aphase difference φ is output.

On the basis of whether the information of the phase difference, i.e.,capacitance component (imaginary component) contained in the detectionsignal 33S falls within the reference range of the phase difference ofan authentic living body, the biometric determination unit 34 determineswhether the object 9 is a living body.

FIGS. 7A and 7B show examples of signal waveforms in amplitudedetection. When a sine wave with its center at the common potential suchas the ground potential is used as the supply signal 31S, the responsesignal 32S changes to an amplitude corresponding to the impedance of theobject 9 with the center at the common potential. The waveforminformation detection unit 33 detects the peak voltage of the responsesignal 32S, i.e., the maximum or minimum value of the voltage, andoutputs the detection signal 33S representing a DC potentialproportional to an amplitude A of the response signal 32S.

On the basis of whether the information of the amplitude, i.e.,resistance component (real component) contained in the detection signal33S falls within the reference range of the amplitude of an authenticliving body, the biometric determination unit 34 determines whether theobject 9 is a living body.

Biometric recognition can be done by detecting only one of the phasedifference and amplitude. For example, a resistive element or capacitiveelement which requires a large area is not always necessary, unlike theprior art. Information representing the impedance unique to the object 9can be detected in detail by a very simple circuit arrangement such as aphase comparison circuit using a general comparator and logic circuit.Hence, size reduction of the surface shape recognition sensor device andon-chip device formation can easily be implemented.

Biometric recognition may be executed by detecting both the phasedifference and amplitude. As compared to a case in which biometricrecognition/determination is done by using information obtained bydetecting the real and imaginary components together, it is verydifficult to individually adjust the real and imaginary components byselecting the material or material properties of the object. Hence, ahigh level of security can be obtained against an illicit recognitionbehavior by using an artificial finger.

Arrangement of Detection Element

The detailed arrangement of the detection elements used in the surfaceshape recognition sensor device according to this embodiment will bedescribed next with reference to FIGS. 8A and 8B. FIGS. 8A and 8B areexplanatory views showing the arrangement of the detection elements.FIG. 8A is a front view, and FIG. 8B is a sectional view taken along aline A-A in FIG. 8A.

Each detection element 1A includes the detection electrode 11A which isarrayed in a grid shape on a sensor surface 8 of the surface shaperecognition sensor device 10 and the detection electrode 12A which isformed into a wall shape at a position spaced apart from the detectionelectrode 11A to surround it. Similarly, each detection element 1Bincludes the detection electrode 11B which is arrayed in a grid shapeand the detection electrode 12B which is formed into a wall shape at aposition spaced apart from the detection electrode 11B to surround it.

The detection electrodes 11A and 11B are formed from a metal film. Theupper side of the detection electrodes in the vicinity of the object 9is covered with an insulating film 14. Each detection electrode forms acapacitive element together with the object 9 serving as a counterdetection electrode. At this time, since the distance between thedetection electrodes changes depending on the three-dimensional patternof the surface shape of the object, an electrostatic capacitancecorresponding to the three-dimensional pattern of the surface shape isformed.

On the other hand, the upper side of the detection electrodes 12A and12B is exposed and comes into contact with the object 9. Accordingly,the common potential connected to the detection electrode 12A is appliedto the object 9. In addition, the impedance of the object 9 is connectedto the biometric recognition unit 3 through the detection electrode 12B.

At this time, the detection electrodes 12A and 12B are shared by theadjacent detection elements 1A and 1B, respectively. A notch 13 isformed between the detection electrodes 12A and 12B at the boundary,where the detection elements 1A and 1B are arranged adjacent, toelectrically insulate the detection electrodes from each other.

When the length of one side of the detection elements 1A and 1B isseveral ten μm, a width W of the notch 13 is set to 20 μm or less. Inthis case, the presence of the notch 13 cannot visually be recognized.Hence, the presence/absence of the biometric recognition detectionelements and their layout positions can be made invisible, and thesecurity level can be increased.

Second Embodiment

A surface shape recognition sensor device according to the secondembodiment of the present invention will be described next withreference to FIG. 9. FIG. 9 is a block diagram showing the arrangementof the surface shape recognition sensor device according to the secondembodiment of the present invention.

In a surface shape recognition sensor device 10, a detection element 1Cis arranged between a detection element 1A and a detection element 1B,unlike the above-described first embodiment (FIG. 2). The remainingparts are the same as in the above-described first embodiment. The samereference numerals as in FIG. 2 denote the same or similar parts in FIG.9.

The detection element 1C has a detection electrode 11C which forms anelectrostatic capacitance with respect to an object 9 through aninsulating film, and a detection electrode 12C which comes intoelectrical contact with the object 9, like the above-described detectionelements 1A and 1B. The detection electrode 11C is connected to asurface shape detection unit 2. The detection electrode 12C is insulatedfrom the remaining potentials. The detection electrode 12C is set in ahigh-impedance (floating) state so that the detection electrode 12C isnot connected to any potential.

The surface shape detection unit 2 outputs surface shape data 2Srepresenting the three-dimensional shape of the surface of the object 9on the basis of the electrostatic capacitances generated betweendetection electrodes 11A, 11B, and 11C of the detection elements 1A, 1B,and 1C.

The biometric recognition unit 3 determines whether the object 9 is aliving body on the basis of the impedance of the object 9 connectedbetween a detection electrode 12B of the detection element 1B and adetection electrode 12A of the detection element 1A.

Since the detection element 1C is arranged between the detectionelectrode 12A and the detection electrode 12B, the distance between themis long. In addition, since the detection electrode 12C which comes intoelectrical contact with the object 9 is set in the high-impedance state,the impedance of the object 9 connected between the detection electrode12A and the detection electrode 12B is higher than that obtained whenthe two detection electrodes are laid out adjacent. Hence, the changeamount of the impedance which changes depending on the object 9increases, and the determination accuracy by the biometric recognitionunit 3 can be increased.

In the example shown in FIG. 9, one detection element 1A, one detectionelement 1B, and one detection element 1C are used. However, this is aminimum arrangement necessary for executing biometric recognition, andthe present invention is not limited to this. Actually, a number ofdetection elements 1A are used to obtain the surface shape datarepresenting the surface shape of the object 9 by the surface shapedetection unit 2. In addition, a number of detection elements 1B areused to stably detect the impedance of the object 9 by the biometricrecognition unit 3. Furthermore, a number of detection elements 1C laidout adjacent are used to increase the change amount of the impedancewhich changes depending on the object 9.

Arrangement of Detection Element

The detailed arrangement of the detection elements used in the surfaceshape recognition sensor device according to this embodiment will bedescribed next with reference to FIGS. 10A and 10B. FIGS. 10A and 10Bare explanatory views showing the arrangement of the detection elements.FIG. 10A is a front view, and FIG. 10B is a sectional view taken along aline B-B in FIG. 10A.

Each detection element 1A includes the detection electrode 11A which isarrayed in a grid shape on a sensor surface 8 of the surface shaperecognition sensor device 10 and the detection electrode 12A which isformed into a wall shape at a position spaced apart from the detectionelectrode 11A to surround it. Similarly, each detection element 1Bincludes the detection electrode 11B which is arrayed in a grid shapeand the detection electrode 12B which is formed into a wall shape at aposition spaced apart from the detection electrode 11B to surround it.The detection electrode 11C includes the detection electrode 11C arrayedin a grid shape and the detection electrode 12C which is formed into awall shape at a position spaced apart from the detection electrode 11Cto surround it.

The detection electrodes 11A, 11B, and 11C are formed from a metal film.The upper side of the detection electrodes in the vicinity of the object9 is covered with an insulating film 14. Each detection electrode formsa capacitive element together with the object 9 serving as a counterdetection electrode. At this time, since the distance between thedetection electrodes changes depending on the three-dimensional patternof the surface shape of the object, an electrostatic capacitancecorresponding to the three-dimensional pattern of the surface shape isformed.

On the other hand, the upper side of the detection electrodes 12A, 12B,and 12C is exposed and comes into contact with the object 9.Accordingly, the common potential connected to the detection electrode12A is applied to the object 9. In addition, the impedance of the object9 is connected to the biometric recognition unit 3 through the detectionelectrode 12B.

At this time, the detection electrodes 12A, 12B, and 12C are shared bythe adjacent detection elements 1A, 1B, and 1C, respectively. A notch 13is formed between the detection electrodes 12A and 12C and between thedetection electrodes 12B and 12C at the boundaries, where the detectionelements 1C and the detection elements 1A and 1B are arranged adjacent,to electrically insulate the detection electrodes from each other.

When the length of one side of the detection elements 1A, 1B, and 1C isseveral ten μm, a width W of the notch 13 is set to 20 μm or less. Inthis case, the presence of the notch 13 cannot visually be recognized.Hence, the presence/absence of the biometric recognition detectionelements and their layout positions can be made invisible, and thesecurity level can be increased.

Third Embodiment

A surface shape recognition sensor device according to the thirdembodiment of the present invention will be described next withreference to FIG. 11. FIG. 11 is a block diagram showing the arrangementof the surface shape recognition sensor device according to the thirdembodiment of the present invention.

In a surface shape recognition sensor device 10, a switch 4C is arrangedbetween the common potential and a detection electrode 12C of adetection element 1C, unlike the above-described second embodiment (FIG.9). The remaining parts are the same as in the above-described secondembodiment. The same reference numerals as in FIG. 9 denote the same orsimilar parts in FIG. 11.

When a surface shape detection unit 2 executes the surface shapedetection operation, the switch 4C is short-circuited to apply thecommon potential to the detection electrode 12C of the detection element1C. When a biometric recognition unit 3 executes the biometricrecognition operation, the switch 4C is opened to set the detectionelectrode 12C of the detection element 1C in a high-impedance state.

Unlike the second embodiment, in the surface shape detection operation,the detection electrode 12C of the detection element 1C is alsoconnected to the common potential, like the detection electrode 11A ofthe detection element 1A. Since clear surface shape data with minimumnoise can be obtained, the authentication accuracy of personalauthentication processing using the surface shape data in the subsequentstage can be increased.

Fourth Embodiment

A surface shape recognition sensor device according to the fourthembodiment of the present invention will be described next withreference to FIGS. 12, 13A, and 13B. FIG. 12 is a block diagram showingthe arrangement of the surface shape recognition sensor device accordingto the fourth embodiment of the present invention. FIGS. 13A and 13B areexplanatory views showing the arrangement of detection elements used inthe surface shape recognition sensor device according to the fourthembodiment of the present invention. FIG. 13A is a front view, and FIG.13B is a sectional view taken along a line C-C.

In a surface shape recognition sensor device 10, an insulating film 14is formed not only on the upper side of a detection electrode 11C of adetection element 1C but also on the upper side of a detection electrode12C, unlike the above-described second embodiment (FIG. 9). In addition,the detection electrode 12C is connected to the common potential. Theremaining parts are the same as in the above-described secondembodiment. The same reference numerals as in FIG. 9 denote the same orsimilar parts in FIG. 12.

Since the detection electrode 12C of the detection element 1C is coveredwith the insulating film 14, the detection electrode 12C is electricallyinsulated from an object 9. Hence, the common potential can always beapplied to the detection electrode 12C. Since clear surface shape datawith minimum noise can be obtained without using the switch 4C of theabove-described third embodiment (FIG. 11), the authentication accuracyof personal authentication processing using the surface shape data inthe subsequent stage can be increased.

Fifth Embodiment

A surface shape recognition sensor device according to the fifthembodiment of the present invention will be described next withreference to FIG. 14. FIG. 14 is a block diagram showing the arrangementof the surface shape recognition sensor device according to the fifthembodiment of the present invention.

In a surface shape recognition sensor device 10, a switch 4B is arrangedbetween a biometric recognition unit 3 and a detection electrode 12B ofa detection element 1B, unlike the above-described first embodiment(FIG. 2). The remaining parts are the same as in the above-describedfirst embodiment. The same reference numerals as in FIG. 2 denote thesame or similar parts in FIG. 14.

In the arrangement in which the biometric recognition unit 3 executesbiometric recognition by applying a signal to an object 9, as in FIG. 5described above, a potential different from the common potential may beapplied to the detection electrode 12B of the detection element 1B, orthe detection electrode 12B may be set in a high-impedance state in thesurface shape detection operation. In such a case, the switch 4B may bearranged between the detection electrode 12B and the biometricrecognition unit 3 to connect the detection electrode 12B to thebiometric recognition unit 3 in the biometric recognition operation andto the common potential in the surface shape detection operation.

With this arrangement, in the surface shape detection operation, thedetection electrode 12B of the detection element 1B is also connected tothe common potential, like a detection electrode 12A of a detectionelement 1A. Since clear surface shape data with minimum noise can beobtained, the authentication accuracy of personal authenticationprocessing using the surface shape data in the subsequent stage can beincreased.

This embodiment has been described on the basis of the first embodiment.However, the fifth embodiment can be applied to any one of theabove-described embodiments, and the same function and effect asdescribed above can be obtained.

Sixth Embodiment

A surface shape recognition sensor device according to the sixthembodiment of the present invention will be described next withreference to FIGS. 15A and 15B. FIGS. 15A and 15B are explanatory viewsshowing the sensor surface structure of the surface shape recognitionsensor device according to the sixth embodiment of the presentinvention.

In the example of the sensor surface structure shown in FIG. 15A, adetection region 8B where a plurality of detection elements 1B used inthe above-described second embodiment (FIG. 9) are arranged adjacent isarranged in a band shape which crosses almost the center of a sensorsurface 8. Detection regions 8C where a plurality of detection elements1C are arranged adjacent are arranged in a band shape on both sides ofthe detection region 8B. Detection regions 8A where a plurality ofdetection elements 1A are arranged adjacent are arranged outside thedetection regions 8C.

The two detection regions 8C are arranged to separate the detectionregions 8A and 8B from each other. The two detection regions 8A arearranged outside the detection regions 8C. The detection region 8B isarranged inside the detection regions 8C. With this structure, even whenthe contact position of an object 9 on the sensor surface 8 may shift inthe horizontal direction from the center of the sensor surface 8, theobject 9 readily contacts both the detection regions 8A and 8B over oneof the detection regions 8C. Hence, a stable biometric recognitionoperation can be executed.

In addition, a width L between the outer edges of the two detectionregions 8C including the detection region 8B is smaller than at least acontact width Lt of the object 9 on the sensor surface 8. With thisstructure, both the detection region 8B and the detection regions 8A onboth sides can simultaneously come into contact with the object 9.Hence, a more stable impedance can be obtained in the biometricrecognition operation.

In the example of the sensor surface structure shown in FIG. 15B, thedetection region 8B where the plurality of detection elements 1B used inthe above-described second embodiment (FIG. 9) are arranged adjacent isarranged in an island shape at almost the center of the sensor surface8. The detection region 8C where the plurality of detection elements 1Care arranged adjacent is arranged in a frame shape which whollysurrounds the periphery of the detection region 8B. The detection region8A where the plurality of detection elements 1A are arranged adjacent isarranged to surround the entire periphery of the detection region 8C.

The detection region 8C is arranged in a frame shape (ring shape) toseparate the detection regions 8A and 8B from each other. The detectionregion 8A is arranged outside the detection region 8C. The detectionregion 8B is arranged inside the detection region 8C. With thisstructure, even when the contact position of the object 9 on the sensorsurface 8 may shift in the vertical and horizontal directions from thecenter of the sensor surface 8, the object 9 readily contacts both thedetection regions 8A and 8B over the detection region 8C. Hence, astable biometric recognition operation can be executed. In this case,the width of the detection region 8C must be smaller than the contactwidth of the object 9 on the sensor surface 8.

In addition, a horizontal width L1 and vertical width L2 between theouter edges of the detection region 8C including the detection region 8Bare smaller than at least a contact horizontal width Lt1 and contacthorizontal width Lt2 of the object 9 on the sensor surface 8,respectively. With this structure, the detection region 8B and thedetection region 8A around it can simultaneously come into contact withthe object 9 at a plurality of points (four points in the vertical andhorizontal directions) or through the entire periphery. Hence, a morestable impedance can be obtained in the biometric recognition operation.

Referring to FIGS. 15A and 15B, a plurality of detection region layoutpatterns may be arranged on the sensor surface 8. In this case, theobject 9 readily contacts both the detection regions 8A and 8B over thedetection region 8C. Hence, a stable biometric recognition operation canbe executed.

In the example shown in FIGS. 15A and 15B, the outside shape of thesensor surface 8 is square, or the detection regions 8A, 8B, and 8C arerectangular or have a square outside shape. However, the presentinvention is not limited to this. For example, a rectangular, circular,or elliptical shape may be used.

In this embodiment, the detection region 8C including the detectionelements 1C is arranged between the detection region 8A and thedetection region 8B on the basis of the above-described secondembodiment (FIG. 9). However, this embodiment can also be applied to thearrangement based on the above-described first embodiment (FIG. 2)without the detection elements 1C.

In this case, on the sensor surface 8, the detection regions 8A and 8Bare arranged adjacent without the detection region 8C in FIGS. 15A and15B. The same function and effect as in the above-described arrangementincluding the detection region 8C can be obtained.

Seventh Embodiment

Arrangement of Biometric Recognition Unit

The detailed arrangement of a biometric recognition unit 3 used in asurface shape recognition sensor device according to still anotherembodiment of the present invention will be described next withreference to FIG. 16. FIG. 16 is a block diagram showing the arrangementof the biometric recognition unit. The same reference numerals as inFIG. 1 or 5 denote the same parts or parts having the same functions inFIG. 16.

The biometric recognition unit 3 includes a supply signal generationunit 31, response signal generation unit 32, waveform informationdetection unit 33, output adjustment unit 34, A/D conversion unit 35,and biometric determination unit 36. Of these circuit units, the supplysignal generation unit 31, response signal generation unit 32, waveforminformation detection unit 33, and output adjustment unit 34 arearranged as an impedance detection unit 30 together with a detectionelement 1B as a pair.

Detection elements 1A and 1B come into electrical contact with an object9 through detection electrodes 12A and 12B to connect a capacitancecomponent Cf and resistance component Rf of the impedance of the object9 to the response signal generation unit 32. The supply signalgeneration unit 31 generates a supply signal 31S such as a sine wave ofa predetermined frequency and outputs it to the response signalgeneration unit 32. The response signal generation unit 32 supplies thesupply signal 31S from the supply signal generation unit 31 to thedetection electrode 12B of the detection element 1B and outputs, to thewaveform information detection unit 33, a response signal 32S whichchanges depending on the output impedance of the detection element 1B,i.e., the capacitance component and resistance component of theimpedance of the object 9.

The waveform information detection unit 33 detects the amplitude or thephase difference of the supply signal 31S as waveform information on thebasis of the waveform indicated by the response signal 32S from theresponse signal generation unit 32 and outputs a waveform informationsignal 33S containing the waveform information to the output adjustmentunit 34. The output adjustment unit 34 adjusts and converts the waveforminformation signal 33S from the waveform information detection unit 33into a voltage value corresponding to the waveform information andoutputs it as a detection signal 30S.

The A/D conversion unit 35 A/D-converts the detection signal 30S fromthe output adjustment unit 34 and outputs it as determination data 35Sformed from digital data. On the basis of the waveform informationcontained in the determination data 35S from the A/D conversion unit 35,the biometric determination unit 36 determines whether the object 9 is aliving body, and outputs a recognition result 3S.

When the object 9 comes into contact with the detection elements 1A and1B, the supply signal 31S applied from the supply signal generation unit31 to the detection elements 1A and 1B changes depending on theimpedance characteristic, i.e., the capacitance component and resistancecomponent unique to the object 9 and is output from the response signalgeneration unit 32 as the response signal 32S. The waveform informationdetection unit 33 detects the amplitude or phase difference of theresponse signal 32S. The detection signal 30S containing the informationrepresenting the detection result is output to the output adjustmentunit 34. The detection signal 30S is converted into the determinationdata 35S by the A/D conversion unit 35 and output to the biometricdetermination unit 36.

FIGS. 17A to 17D show examples of signal waveforms in phase differencedetection. When a sine wave with its center at the common potential suchas the ground potential is used as the supply signal 31S, the phase ofthe response signal 32S changes in accordance with the impedance of theobject 9. When a signal synchronized with the supply signal 31S is usedas the reference signal, and its phase is compared with the phase of theresponse signal 32S by the waveform information detection unit 33, thewaveform information signal 33S having a pulse width corresponding to,e.g., a phase difference φ is output.

On the basis of whether the information of the phase difference, i.e.,capacitance component (imaginary component) contained in thedetermination data 35S falls within the reference range of the phasedifference of an authentic living body, the biometric determination unit36 determines whether the object 9 is a living body.

FIGS. 18A and 18B show examples of signal waveforms in amplitudedetection. When a sine wave with its center at the common potential suchas the ground potential is used as the supply signal 31S, the responsesignal 32S changes to an amplitude corresponding to the impedance of theobject 9 with the center at the common potential. The waveforminformation detection unit 33 detects the peak voltage of the responsesignal 32S, i.e., the maximum or minimum value of the voltage, andoutputs the waveform information signal 33S representing a DC potentialproportional to an amplitude A of the response signal 32S.

On the basis of whether the information of the amplitude, i.e.,resistance component (real component) contained in the determinationdata 35S falls within the reference range of the amplitude of anauthentic living body, the biometric determination unit 36 determineswhether the object 9 is a living body.

Biometric recognition can be done by detecting only one of the phasedifference and amplitude. For example, a resistive element or capacitiveelement which requires a large area is not always necessary, unlike theprior art. Information representing the impedance unique to the object 9can be detected in detail by a very simple circuit arrangement such as ageneral comparator and logic circuit. Hence, size reduction of thesurface shape recognition sensor device and on-chip device formation caneasily be implemented.

Biometric recognition may be executed by detecting both the phasedifference and amplitude. As compared to a case in which biometricrecognition/determination is done by using information obtained bydetecting the real and imaginary components together, it is verydifficult to individually adjust the real and imaginary components byselecting the material or material properties of the object. Hence, ahigh level of security can be obtained against an illicit recognitionbehavior by using an artificial finger.

In the above-described example, one impedance detection unit 30 is used.However, the present invention is not limited to this. A plurality ofimpedance detection units 30 may be arranged. In this case, for example,the A/D conversion unit 35 is arranged for each impedance detection unit30. A plurality of determination data 35S obtained from the A/Dconversion units 35 are averaged, and the biometric determination unit36 executes biometric determination on the basis of the average value.Alternatively, a control unit 25 may sequentially select each impedancedetection unit 30, and the detection signal 30S from each impedancedetection unit 30 may sequentially be converted into determination databy the single A/D conversion unit 35. The supply signal generation unitneed not always be arranged in the impedance detection unit. In thiscase, the impedance detection unit can be made compact, and the area forfingerprint detection can be increased.

As described above, when the plurality of impedance detection units 30are arranged, the detection results obtained by the impedance detectionunits 30 are averaged. Since the impedance detection accuracy can beincreased, the security level for illicit authentication by using anartificial finger can be increased.

Eighth Embodiment

A surface shape recognition sensor device according to the eighthembodiment of the present invention will be described next withreference to FIG. 19. FIG. 19 is a block diagram showing the arrangementof the surface shape recognition sensor device according to the eighthembodiment of the present invention. The same reference numerals as inthe above-described drawings denote the same or similar parts in FIG.19.

In a sensor array 4 of a surface shape recognition sensor device 10, aplurality of capacitance detection units 20 for surface shape detectionare arranged in a grid shape (matrix) together with detection elements1A as pairs. In place of one of the capacitance detection units 20, andin this example, the capacitance detection unit 20 arranged at thecenter of the sensor array 4, an impedance detection unit 30 forbiometric recognition is arranged together with a detection element 1Bas a pair.

A control unit 25, column selector 26, A/D conversion unit 27, and rowselector 28 are circuit units which form a surface shape detection unit2 described above together with each capacitance detection unit 20. AnA/D conversion unit 35 and biometric determination unit 36 are circuitunits which form a biometric recognition unit 3 described above togetherwith the impedance detection unit 30.

The surface shape recognition sensor device 10 is formed from one chipas a whole. The capacitance detection units 20 and impedance detectionunit 30 are formed at positions corresponding to the detection elements1A and 1B in the sensor array 4 on the substrate. An interlayerdielectric film is formed on the resultant structure, and the detectionelements 1A and 1B are formed on it. The control unit 25, columnselector 26, A/D conversion unit 27, and row selector 28, and the A/Dconversion unit 35 and biometric determination unit 36 are formed aroundthe formation region of the capacitance detection units 20 and impedancedetection unit 30, i.e., in the vacant peripheral region on thesubstrate.

Of the capacitance detection units 20, the capacitance detection units20 arrayed in the column direction (vertical direction) are connected tothe column selector 26 through a single control line 26L correspondingto the column. In addition, the capacitance detection units 20 arrayedin the row direction (horizontal direction) are connected to the A/Dconversion unit 27 through a single data line 20L corresponding to therow. The impedance detection unit 30 is connected to the control unit 25through an individual control line 25L and also connected to the A/Dconversion unit 35 through an individual data line 30L.

The operation of the surface shape recognition sensor device accordingto this embodiment will be described next.

In executing the surface shape detection operation of detecting thesurface shape of an object 9 under the control of a host apparatus (notshown), the control unit 25 outputs an address signal 25A andcapacitance detection control signal 25B at predetermined timings.

The column selector 26 sequentially selects one of the control lines 26Lon the basis of the address signal 25A and capacitance detection controlsignal 25B.

Accordingly, the above-described capacitance detection is done by eachselected capacitance detection unit 20. A capacitance signal 20S isoutput to the corresponding data line 20L.

The A/D conversion unit 27 A/D-converts the capacitance signal 20S,which is output from each capacitance detection unit 20 selected by thecolumn selector 26 to the data line 20L, into three-dimensional data 27Sand outputs it. The row selector 28 sequentially selects thethree-dimensional data 27S obtained from the A/D conversion unit 27 foreach data line 20L and outputs surface shape data 2S representing thesurface shape of the object 9.

In executing the biometric recognition operation of determining whetherthe object 9 is a living body under the control of the host apparatus,the control unit 25 selects the individual control line 25L at apredetermined timing. The above-described impedance detection is done bythe selected impedance detection unit 30, and a detection signal 30S isoutput to the corresponding individual data line 30L.

The A/D conversion unit 35 A/D-converts the detection signal 30S outputfrom the impedance detection unit 30 to the individual data line 30Linto determination data 35S and outputs it. On the basis of whether theinformation representing the phase difference or amplitude contained inthe determination data 35S falls within the reference range of the phasedifference or amplitude of an authentic living body, the biometricdetermination unit 36 determines whether the object 9 is a living body.

As described above, in this embodiment, the capacitance detection units20 for surface shape detection are arranged in a matrix on the sensorarray 4 together with the detection elements 1A. In place of one of thecapacitance detection units 20, the impedance detection unit 30 forbiometric recognition is arranged together with the detection element1B. With this arrangement, the interconnection which connects thedetection element 1B for biometric recognition to the impedancedetection unit 30 to drive the detection element can be very short.Since the parasitic capacitance or noise of this interconnection can bereduced, the impedance of the object can accurately be detected. Hence,a high determination accuracy can be obtained in biometric recognition.

In the impedance detection unit 30, a predetermined supply signal isapplied to the detection element 1B. A signal whose phase and amplitudehave changed in accordance with the impedance of the object is acquiredas a response signal. Waveform information containing the phase oramplitude representing the waveform of the response signal is detectedand output as the detection signal 30S. The detection signal 30S isA/D-converted into the determination data 35S by the A/D conversion unit35. Then, determination is done by the biometric determination unit 36on the basis of the determination data 35S. For example, a resistiveelement or capacitive element which requires a large area is not alwaysnecessary, unlike the prior art. Information representing the impedanceunique to the object 9 can be detected in detail by a very simplecircuit arrangement such as a general comparator and logic circuit.Hence, size reduction of the surface shape recognition sensor device andon-chip device formation can easily be implemented. In addition, theexternal component such as a resistive element or capacitive element isunnecessary. Since any decrease in security level caused by the externalcomponent can be avoided, sufficient security can be obtained.

Ninth Embodiment

A surface shape recognition sensor device according to the ninthembodiment of the present invention will be described next withreference to FIG. 20. FIG. 20 is a block diagram showing the arrangementof the surface shape recognition sensor device according to the ninthembodiment of the present invention. The same reference numerals as inFIG. 19 denote the same or similar parts in FIG. 20.

In this embodiment, an A/D conversion unit 27 also serves as an A/Dconversion unit 35, unlike the above-described eighth embodiment (FIG.19).

In this case, not an individual data line 30L but a data line 20L whichconnects capacitance detection units 20 arranged in the same column asan impedance detection unit 30 is connected to the impedance detectionunit 30. When a control unit 25 selects an individual control line 25Lin the biometric recognition operation, the above-described impedancedetection is done by the impedance detection unit 30, and a detectionsignal 30S is output to the corresponding data line 20L.

The A/D conversion unit 27 A/D-converts the detection signal 30S outputfrom the impedance detection unit 30 to the data line 20L intodetermination data 35S and outputs it. The determination data 35S isoutput from a row selector 28 to a biometric determination unit 36.

As described above, the A/D conversion unit 27 used in the surface shapedetection operation is also used in the biometric recognition operation.Since the A/D conversion unit 35 for the biometric recognition operationcan be omitted, the chip area and manufacturing cost can be reduced.

In addition, since the individual data line 30L is unnecessary, the chiparea can be reduced. Especially, when a plurality of impedance detectionunits 30 are arranged, the effect of omitting the individual data line30L is large because the individual data line 30L is necessary for eachimpedance detection unit 30.

10th Embodiment

A surface shape recognition sensor device according to the 10thembodiment of the present invention will be described next withreference to FIG. 21. FIG. 21 is a block diagram showing the arrangementof the surface shape recognition sensor device according to the 10thembodiment of the present invention. The same reference numerals as inFIG. 20 denote the same or similar parts in FIG. 21.

In this embodiment, a control line 26L also serves as an individualcontrol line 25L, unlike the above-described ninth embodiment (FIG. 20).

In this case, not the individual control line 25L but the control line26L which connects capacitance detection units 20 arranged in the samecolumn as an impedance detection unit 30 is connected to the impedancedetection unit 30. In the biometric recognition operation, on the basisof an address signal 25A and capacitance detection control signal 25Bfrom a control unit 25, a column selector 26 selects the control line26L connected to the impedance detection unit 30, and theabove-described impedance detection is done.

As described above, the control line 26L is also used as the individualcontrol line 25L. Since the individual control line 25L can be omitted,the chip area can be reduced. Especially, when a plurality of impedancedetection units 30 are arranged, the effect of omitting the individualcontrol line 25L is large because the individual control line 25L isnecessary for each impedance detection unit 30.

In executing the above-described embodiments, when biometric recognitionis done by using a plurality of impedance detection units 30,appropriate embodiments may be selected and combined for each impedancedetection unit 30.

For example, depending on the layout positions of individual impedancedetection units 30 or the layout number of impedance detection units 30,the vacant region to form the individual control line 25L or individualdata line 30L cannot be ensured in some cases. For the impedancedetection units 30, the data line 20L of the capacitance detection units20 may also serve as the individual data line 30L by using the secondembodiment. Alternatively, the control line 26L or data line 20L of thecapacitance detection units 20 also serves as the individual controlline 25L or individual data line 30L by using the third embodiment.Accordingly, the impedance detection units can be laid out at desiredpositions without being limited by the vacant region.

When the individual control line 25L is used as in the ninth embodiment,the entire column selector 26 need not be operated in the biometricauthentication operation. Hence, the power consumption and noise in theentire device can be reduced. When the individual data line 30L andindividual control line 25L are used as in the 10th embodiment, theentire column selector 26 and the entire A/D conversion unit 27 need notbe operated in the biometric authentication operation. Hence, the powerconsumption and noise in the entire device can further be reduced.

1. A surface shape recognition sensor device characterized bycomprising: a plurality of capacitance detection units which arearranged in a grid shape to cause a detection element to detect acapacitance generated with respect to an object and output a capacitancesignal representing a value of the capacitance; detection elements whichare arranged near said capacitance detection units; a plurality ofcontrol lines which connect, of said capacitance detection units,capacitance detection units arranged in a column direction; a pluralityof data lines which connect, of said capacitance detection units,capacitance detection units arranged in a row direction; a columnselector which sequentially selects one of said control lines to selecteach capacitance detection unit connected to said control line; a firstA/D conversion unit which is arranged for each data line andA/D-converts the capacitance signal, which is output from eachcapacitance detection unit selected by said column selector to said dataline, into three-dimensional data and outputs the three-dimensionaldata; a row selector which sequentially selects the three-dimensionaldata obtained from said first A/D conversion unit for each data line andoutputs the three-dimensional data as surface shape data representing asurface shape of the object; an impedance detection unit which isarranged together with a detection element as a pair in place of one ofsaid capacitance detection units and comes into electrical contact withthe object through said detection element to detect an impedance of theobject and outputs a detection signal corresponding to the impedance;and a biometric determination unit which determines on the basis of thedetection signal from said impedance detection unit whether the objectis a living body, wherein said biometric recognition unit comprises aresponse signal generation unit which applies a predetermined supplysignal to said detection element and outputs, as a response signal, asignal whose phase and amplitude have changed in accordance with animpedance of the object which is in electrical contact through saiddetection element, and a waveform information detection unit whichdetects, as waveform information, one of the phase and amplituderepresenting a waveform of the response signal and outputs a detectionsignal representing the waveform information, and said biometricdetermination unit executes determination on the basis of whether thewaveform information contained in the detection signal falls within areference range of the waveform information which indicates an authenticliving body.
 2. A surface shape recognition sensor device according toclaim 1, characterized by further comprising an individual control linewhich is connected to said impedance detection unit, an individual dataline which is connected to said impedance detection unit, a control unitwhich selects said impedance detection unit by selecting said individualcontrol line, and a second A/D conversion unit which outputs, asdetermination data, the waveform information contained in the detectionsignal output from said impedance detection unit to said individual dataline, wherein said impedance detection unit outputs the detection signalrepresenting the waveform information corresponding to the impedance ofthe object to said individual data line in accordance with selection bysaid control unit through said individual control line, and saidbiometric determination unit executes determination on the basis of thewaveform information contained in the determination data from saidsecond A/D conversion unit.
 3. A surface shape recognition sensor deviceaccording to claim 1, characterized by further comprising an individualcontrol line which is connected to said impedance detection unit, and acontrol unit which selects said impedance detection unit by selectingsaid individual control line, wherein said impedance detection unit isconnected to one of said data lines and outputs the detection signalrepresenting the waveform information corresponding to the impedance ofthe object to said data line in accordance with selection by saidcontrol unit through said individual control line, and said biometricdetermination unit executes determination on the basis of the waveforminformation contained in determination data which is obtained by causingsaid first A/D conversion unit to A/D-convert the detection signaloutput to said data line.
 4. A surface shape recognition sensor deviceaccording to claim 1, characterized in that said impedance detectionunit is connected to one of said control lines and one of said datalines and outputs the detection signal to said data line in accordancewith selection by said selector, and said biometric determination unitexecutes determination on the basis of the waveform informationcontained in determination data which is obtained by causing said firstA/D conversion unit to A/D-convert the detection signal output to saiddata line.
 5. A surface shape recognition sensor device according toclaim 1, characterized by further comprising a plurality of saidimpedance detection units which are arranged in place of different saidcapacitance detection units.